Recently, a three-dimensional two scale damage model has been proposed for high cycle fatigue applications. The model takes into account plasticity and damage at the microscale and the behavior is considered as elastic at the mesoscale. In this paper, a robust numerical algorithm of the two scale damage model has been implemented. The explicit stress update scheme is performed for the model. This model can be used to predict failure for any kind of loading, cycle or random, mechanical,and thermo-mechanical. The cylindrical pipe subjected to complex thermo-mechanical fatigue loading and the helicopter main rotor shaft subjected to non-proportional loading are investigated by the two scale damage model.